MySQL - subquery in WHERE unknown column in join (count in subquery)

Question

The following query is giving me this error:

Error Code: 1054. Unknown column 'jobs.id' in 'on clause'


SELECT clinics.id as cid, clinics.name, clinics.address AS clinicAddress,
            clinics.post_code as clinicZip, clinics.city AS clinicCity, clinics.region,
            countries.full_name AS country,
            jobs.name AS jobName, jobs.created_at AS jobCreatedAt, jobs.from AS jobStarts,
            jobs.description AS jobDescription, jobs.rates, jobs.max_applicants, jobs.created_at,
            locum_types.name AS locumName,
            job_statuses.name AS statusName,
            CONCAT(users.first_name, ' ', users.last_name) AS userName, users.title AS userTitle,
            roles.name AS roleName            
            FROM clinics
            JOIN countries ON countries.id = clinics.country_id
            JOIN jobs ON clinics.id = jobs.clinics_id
            JOIN users ON users.id = jobs.users_id
            JOIN roles ON roles.id = users.roles_id
            JOIN locum_types ON locum_types.id = jobs.locum_types_id
            JOIN job_statuses ON job_statuses.id = jobs.statuses_id
            WHERE (LOWER(`clinics`.`city`) like '%abbey%'
            OR LOWER(`clinics`.`post_code`) like '%abbey%'
            OR LOWER(`clinics`.`region`) like '%abbey%')
            AND jobs.to >= '2020-01-31 07:53:48'
            AND applicants IN (SELECT COUNT(user_jobs_application.id) as applicants 
                FROM user_jobs_application
                JOIN user_jobs_application as jobApplication ON user_jobs_application.jobs_id = jobs.id
                HAVING applicants < jobs.max_applicants)
            LIMIT 20 OFFSET 0

I am trying to count all jobs in the user_jobs_application table and check if the count is lesser than the max_applicants in jobs table.

The structure of the jobs table is following:

id
max_applicants
created_at

The user_jobs_application table (this is pivot table):

id
users_id
jobs_id

Basically I need to count all applications for the job and check if it within limits ( max_applicants ). Any idea what am I doing wrong here?

Answer 1

Try :

JOIN user_jobs_application as jobApplication ON user_jobs_application.id = jobs.id

Instead of :

JOIN user_jobs_application as jobApplication ON user_jobs_application.jobs_id = jobs.id

Answer 2

The sub-query that you did after applicants IN is being treated separately from the outer query so it doesn't "see" the jobs table as it is out of it's scope.

Why don't you start with a simple query first. Just to get the result you wanted. Focus on the two tables only. You might use a query like below:

SELECT jobs.id, jobs.max_applicants, uja.jobs_id, uja.total_applicants 
FROM   jobs 
JOIN   (SELECT jobs_id,COUNT(*) total_applicants FROM user_jobs_application GROUP BY jobs_id) uja
ON     uja.jobs_id = jobs.id
WHERE  jobs.to >= '2020-01-31 07:53:48'
AND    uja.total_applicants > jobs.max_applicants;

Make the count from user_jobs_application table into a sub-query then join it with jobs table. See if this can return the result you wanted. If it does, then you can implement this into your original query. Probably something like this:

SELECT clinics.id AS cid, clinics.name, clinics.address AS clinicAddress,
            clinics.post_code AS clinicZip, clinics.city AS clinicCity, clinics.region,
            countries.full_name AS country,
            jobs.name AS jobName, jobs.created_at AS jobCreatedAt, jobs.from AS jobStarts,
            jobs.description AS jobDescription, jobs.rates, jobs.max_applicants, jobs.created_at,
            locum_types.name AS locumName,
            job_statuses.name AS statusName,
            CONCAT(users.first_name, ' ', users.last_name) AS userName, users.title AS userTitle,
            roles.name AS roleName            
            FROM clinics
            JOIN countries ON countries.id = clinics.country_id
            JOIN jobs ON clinics.id = jobs.clinics_id
            JOIN users ON users.id = jobs.users_id
            JOIN roles ON roles.id = users.roles_id
            JOIN locum_types ON locum_types.id = jobs.locum_types_id
            JOIN job_statuses ON job_statuses.id = jobs.statuses_id
            /*Insert here*/
            JOIN 
            (SELECT jobs_id,COUNT(*) total_applicants 
             FROM   user_jobs_application GROUP BY jobs_id) uja ON  uja.jobs_id = jobs.id
            /**/      
            WHERE (LOWER(`clinics`.`city`) LIKE '%abbey%'
            OR LOWER(`clinics`.`post_code`) LIKE '%abbey%'
            OR LOWER(`clinics`.`region`) LIKE '%abbey%')
            AND jobs.to >= '2020-01-31 07:53:48'
            /*and add the condition here*/
            AND uja.total_applicants > jobs.max_applicants
            /**/
            LIMIT 20 OFFSET 0;